服务使程序实现后台运行,服务一般包含线程,线程依赖于应用进程,同理服务也是依赖
每一个创建该服务的应用进程,每一个打开的应用程序可以成为一个进程。
可成为一个进程,服务并不会自动开启线程,所有的代码都是默认在主线程里面运行的,
所以一般是在服务里面创建子线程,否则就可能出现主线程被阻塞的情况。
Android线程:
如果想进行UI操作,在子线程里是不能实现的,必须到主线程才能实现,一般在子线程
进行hanlder.sendMessage(message)—–然后在handler里进行逻辑操作
private Handler handler = new Handler(){
public void handleMessage(Message msg){
//逻辑操作
}
};
线程信息的处理机制图:
Sevice(服务):
服务的生命周期:onBind(),onCreate(),onStartCommand(),onDestroy()
public class MyService extends Service {
private DownLoadBinder mBinder = new DownLoadBinder();
//实现活动和服务的通信或者使联系更紧密
//创建一个实例,然后再onBind()里面返回一个实例,然后再MainActivity中
//新建ServiceConnection对象,在这对象里面重写两个方法,实现对mBlid
//实例的调用
class DownLoadBinder extends Binder{
public void startDownload(){
Log.d("MyService", "startDownload");
}
public int getProgress(){
Log.d("MyService", "getProgress");
return 0;
}
}
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return mBinder;
}
@Override
public void onCreate(){
super.onCreate();
//前台服务用法
Notification notification = new Notification(R.drawable.ic_launcher, "Notification",
System.currentTimeMillis());
Intent notificationItent = new Intent(this,MainActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notificationItent,0 );
notification.setLatestEventInfo(this, "This is Title", "This is content",pendingIntent );
//设置到通知栏显示一个前台服务
//这个时候的前台服务和通知有个很大的区别
//即服务不能一拉消除而通知可以
startForeground(1, notification);
Log.d("MyService", "onCreate executed");
}
@Override
public int onStartCommand(Intent intent,int flags,int startId){
Log.d("MyService", "onStartCommand executed");
return super.onStartCommand(intent, flags, startId);
//逻辑操作,在这里一般创建子线程
}
@Override
public void onDestroy(){
super.onDestroy();
Log.d("MyService", "onDestroy executed");
}
}
public class MainActivity extends Activity implements OnClickListener{
private Button startService;
private Button stopService;
private Button startIntentService;
//实现活动和服务的联系即是绑定服务
private Button blind;
private Button Unblind;
//由于定义了一个内部类,所以要调用内部类的对象则
private MyService.DownLoadBinder downLoadBinder;
//然后还要通过一个ServiceConnection 实现对两个方法的调用
//serviceConnection,在绑定和解绑服务传入
private ServiceConnection serviceConnection = new ServiceConnection() {
@Override
public void onServiceDisconnected(ComponentName name) {
// TODO Auto-generated method stub
// Log.d("MyService", "unblinder OK");
}
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
// TODO Auto-generated method stub
downLoadBinder = (MyService.DownLoadBinder)service;
downLoadBinder.startDownload();
downLoadBinder.getProgress();
}
};
@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main_activity);
startIntentService = (Button)findViewById(R.id.intent_service_button);
startService = (Button)findViewById(R.id.start_service_button);
stopService = (Button)findViewById(R.id.stop_service_button);
blind = (Button)findViewById(R.id.bind_service_button);
Unblind = (Button)findViewById(R.id.ubind_service_button);
startService.setOnClickListener(this);
stopService.setOnClickListener(this);
blind.setOnClickListener(this);
Unblind.setOnClickListener(this);
startIntentService.setOnClickListener(this);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch(v.getId()){
case R.id.start_service_button:
Intent startIntent = new Intent(this,MyService.class);
//开启服务
startService(startIntent);
Toast.makeText(this, "开启服务", Toast.LENGTH_SHORT).show();
break;
case R.id.stop_service_button:
Intent stopIntent = new Intent(this,MyService.class);
stopService(stopIntent);
Toast.makeText(this, "关闭服务", Toast.LENGTH_SHORT).show();
break;
case R.id.bind_service_button:
Intent bindIntent = new Intent(this,MyService.class);
bindService(bindIntent, serviceConnection, BIND_AUTO_CREATE);
//绑定服务
break;
case R.id.ubind_service_button:
//解绑服务
unbindService(serviceConnection);
break;
case R.id.intent_service_button:
Log.d("MainActivity", "Thread id is "+Thread.currentThread().getId());
Intent intentService = new Intent(this,MyIntentService.class);
startService(intentService);
break;
default:
break;
}
}
}
标准服务案例:
定时启动服务,实现定时操作
//AlarmManager对象
LongService extends Service{
onStartCommand(){
new Thread(new Runnable(){
@Override
public void run(){
}
}).start();
}
}
//这里是实现的是定时执行任务,只要把任务
Log.d("LongRunningService", "executed at "+new Date().toString());替换就可以
public class LongRunningService extends Service {
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId){
new Thread(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
//执行任务
Log.d("LongRunningService", "executed at "+new Date().toString());
}
}).start();
//AlarmManager 对象
AlarmManager manager = (AlarmManager)getSystemService(ALARM_SERVICE);
int laytime = 6*1000;
long triggerAtTime = SystemClock.elapsedRealtime()+laytime;
Intent i = new Intent(this,AlarmReceiver.class);
PendingIntent pi = PendingIntent.getBroadcast(this, 0, i, 0);
//定时时间从系统开机开始,唤醒CPU
manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP,triggerAtTime , pi);
//在这里的执行到广播接收器里面开启了新的服务,然后在广播接收器和LongRunningService不断循环不断执行任务
return super.onStartCommand(intent, flags, startId);
}
}
public class AlarmReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
Intent i = new Intent(context,LongRunningService.class);
context.startService(i);
}
}
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
Intent i = new Intent(this,LongRunningService.class);
startService(i);
}
}
//别忘了在
<application>
<service android:name=".LongRunningService"></service>
<receiver android:name=".AlarmReceiver"></receiver>
</application>
分析: 首先从MainActivity开始启动
Intent i = new Intent(this,LongRunningService.class);
startService(i);
在LongRunningService.class启动了AlarmReceiver
在AlarmReceiver中又启动了LongRunningService.class
这样不断循坏开始